Waxes are easily moldable substances, mostly insoluble in water and soluble in some organic solvents. Whether natural or synthetic, waxes are chemically very stable mixtures composed of molecules of hydrocarbons and esters of fatty acids. Natural waxes also contain fatty alcohol, whereas synthetic waxes contain hydrocarbons and polyetheroxides.
Natural waxes are said to be natural because they are derived from natural substances however manufactured by humans. Among the natural waxes, we find three kinds of waxes:
– Natural mineral waxes so called because they are extracted from the subsoil like minerals but they are nevertheless formed of organic molecules.
– Natural plant waxes- substances produced naturally by plants
– Natural animal waxes- natural substances produced by animals
Synthetic waxes have been synthesized by humans, and they are created due to chemical reactions.
Natural mineral waxes
Paraffin and micro-crystalline waxes
During the distillation of crude oils, a cut corresponding to paraffins and waxes is obtained in a temperature zone ranging between 400 ° C. and 500 ° C.
These are saturated hydrocarbons with carbon numbers between 18 and 60.
Micro-crystalline mineral waxes have long, branched chains which gives them a microcrystalline structure, hence their name. The result is a soft, white, non-translucent substance with a melting point above 70 ° C.
Paraffins have slightly shorter and linear chains (unbranched) which gives them a macrocrystalline structure. The result is a white solid, translucent, rigid and easily broken, with a fairly low melting point (between 50 and 70 ° C).
Among the less well-known mineral natural waxes, we also find waxes of a structure similar to those obtained from petroleum, in lignites (coals with approximately 75% carbon); they are called ozocerites.
Lastly, there are the montan waxes which are mineral waxes obtained from fossilized plants, which can be extracted from coals and lignites. These Montan waxes are very hard, and this hardness is due to the high concentration of fatty acids and free alcohols and to the low concentration of esters (it is these esters which predominate in soft waxes). They are dark and fragrant when extracted but can be purified for commercialization; it is found in certain polishes, in certain inks, in leather care products and in the manufacture of carbon papers. They also constitute the food additive noted E912 (glazing agent).
The uses of natural mineral waxes are numerous:
– in the field of cosmetics where they serve as an excipient, sometimes as a thickener, as a texturizing or film-forming agent, and lastly they are also used for hair removal.
– they are used to maintain and shine certain woods (furniture, parquet floors), and they are encaustic as well.
– in the food industry: certain cheeses and certain fruits are wrapped in wax to preserve them; some candies are coated to make them shiny; and chewing gum has a wax-based consistency agent.
– to manufacture inks and give them shine as well as to modify their mechanical properties.
– in the paper industry (especially food packaging).
– for the maintenance of leather, where waxes are used in the form of polishes.
– to make candles.
Natural waxes from plants
Natural plant or animal waxes are part of a group of compounds called cerides which are a subset of a larger set of substances called lipids; which are esters of fatty acids and fatty alcohols.
Natural fatty acids are straight chain saturated or unsaturated carboxylic acids, the most important of which contain 12 to 22 even numbered carbon atoms.
Several data characterize natural waxes and provide information on their composition:
The acid number: which reflects the quantity of free acids in the wax; the mass of potash (potassium hydroxide (KOH) in mg fixed cold by 1g of this wax. This index provides information on the acidity of the wax, which is a character that can have an impact on the support which receives it.
The saponification number and ester number: The saponification number is the mass (in mg) of KOH required to saponify 1 g of the fatty substance when hot. The difference between the saponification number and acid number gives the ester number which provides information on the importance of esters in the composition of the wax.
The iodine number. This is the mass of halogen expressed in grams, calculated as I2 attached to the double bonds of 100g of wax. It makes it possible to determine the degree of unsaturation of the wax, that is to say the number of carbon-carbon double bonds which exist in the chains of fatty acids and fatty alcohols which compose it.
- Carnauba wax
This wax comes from Copernicia cerifera (common name Copernicia prunifera) a palm tree 10 to 12m high. Its large green fan-shaped leaves are coated with this wax which is also called Brazilian wax because these trees grow well in the northeast of the country. Each tree yields approximately 7 kgs of of wax.
It represents about 60% of vegetable waxes used in industry and comes almost exclusively from Brazil.
Carnauba wax is a hard, brittle solid wax with a resinous fracture, and is light brown to pale yellow in color. On the market, it comes in powder or flakes.
This wax is practically insoluble in water and in ethanol.
Carnauba wax is a little more heat resistant than beeswax, and it melts around 85 ° C.
Its acidity index varies from 2 to 7, so it is a slightly more acidic wax; its iodine number is 10, so few unsaturations; its saponification index varies from 78 to 95.
Its food code is E903, its specific gravity is 0.97.
Carnauba wax is used in combination with other waxes and in particular with beeswax for the manufacture:
– encaustics (we speak of encaustic when the wax is mixed in solution in a solvent such as turpentine)
– leather care polishes
-cosmetics to make make-up such as lipsticks
and also :
– in the food industry (coating of chewing gum)
– in the paper industry to make oiled paper (translucent) …
- Jojoba wax
This comes from Simmondsia chinensis, a shrub native to the deserts of Arizona and northwestern Mexico.
This wax is an oily-looking liquid (sometimes incorrectly called jojoba oil), quite viscous, slightly yellowish, odorless, obtained by pressing the seeds of the plant.
Jojoba wax contains approximately 97% unsaturated ceridic esters.
Its acidity index is less than 1, so it is a wax with very few free fatty acids; its iodine number is 80 to 85 so a lot of unsaturations, and its saponification index varies from 88 to 96.
Jojoba wax is mainly used in cosmetics for skin care (soaps, moisturizers, sunscreens), but also for hair (shampoos).
- Candelilla wax
The stems and leaves of a plant growing in northeastern Mexico and southern Texas (Euphorbia cerifera or Euphorbia antisyphilitica) are coated with this, and it is collected by treating the plant with hot water acidulated with sulfuric acid.
Candelilla wax is a hard solid (but less hard than carnauba wax), with a density between 0.95 and 0.99. It’s more or less yellow-brown in color, translucent, and whose melting point is around 70 ° C. It is insoluble in water, very slightly soluble in ethanol, soluble in acetone, benzene, gasolines and oils.
Candelilla wax is relatively waterproof, and its primary function being to limit the evaporation of water from the plant on which it is found, and which grows in almost desert-like regions.
Its acidity index is between 12 and 15; its iodine number between 30 and 35; its saponification index between 50 and 65.
It is used in cosmetic products and in particular lipsticks and solid sticks to limit the dehydration of the lips. This wax is hard but it can be mixed with liquid jojoba wax, which makes it possible to obtain the consistency desired.
Candelilla wax is also used in the manufacture of candles (hence its name, in Spanish) and lubricants, leather care products, products for waterproofing papers.
It is a food additive whose code is E902, used as a coating agent (confectionery, chewing gum, etc.).
- Rice bran wax
Rice (Oriza sativa) is contained in a very thin inedible shell called rice bran.
From rice bran it is possible to extract oil and wax by solvent.
Rice bran wax is an orange-yellow solid, odorless, which melts at around 78 ° C.
It is essentially composed of esters of fatty acids and fatty alcohols.
Its acidity index is around 10; its iodine number, about 20, and its saponification index between 75 and 120.
It is used in cosmetics, as an emollient, as an exfoliant, as a film-forming or thickener and as a hardener in lipsticks.
It is a food additive whose code is E908, used as a coating agent (confectionery, chewing gum, etc.).
This is also found in other sectors of industry: pharmaceutical products, printing inks, lubricants, etc.
- Soy wax, rapeseed, coconut, palm, sunflower
These vegetable waxes are obtained from the hydrogenation of natural vegetable oils.
Hydrogenation is a chemical reaction that involves the addition of one molecule of hydrogen (H2) to another compound. This reaction is usually employed to reduce or saturate organic compounds. It generally requires catalysis, however if this isn’t the case ; reactions without catalysis require very high temperatures.
Natural waxes from animals
- Beeswax
Beeswax is produced from the wax glands located on the ventral side of the abdomen of worker bees (the queen and males do not produce it), in the form of thin transparent white scales. This wax mixed with bee saliva is then kneaded by the mandibles, brought to a temperature of around 35 ° C and is used for the construction of hexagonal cells. Namely that this perfectly hexagonal shape of the cells is not the fact of the bees; bees actually build cylinders, and the physical laws that govern the behavior of grouped cylinders, formed of a solid substance that softens at a certain temperature (viscosity, surface tension, etc.) do the rest. It is in these cells that the honey will be deposited, another layer of wax then sealing the cells.
It is from honey and sugars that the bee synthesizes wax and not from pollen.
Beeswax is an initially white solid but which gradually turns brown under the effect of the pigments of several substances including pollen. This wax melts around 65 ° C and its density is 0.96. It is insoluble in water, but soluble in hot ethanol, chloroform and benzene.
Its acidity index is between 15 and 23; its iodine number between 6 and 12; its saponification number between 85 and 105 and its ester number between 70 and 82.
Beeswax is used in cosmetics where its film-forming power is used in lipsticks and deodorant sticks, its texturizing power in glosses and its hardening power in soaps.
Beeswax is also used in the pharmaceutical industry; it is also used to make candles; in the food industry it is used as a coating agent and it is a food additive classified under code E 901 (texture and glazing agent). Finally, so-called “natural” polishes contain it often mixed with carnauba wax.
- Whale white (or spermaceti)
Spermaceti is a white, odorless, oily-looking compound which melts at a temperature above 30 ° C, insoluble in water but soluble in hot ethanol, chloroform and xylene.
Up to 4 tonnes of this mixture can be found in the head of a large sperm whale. The role of this substance is not fully established, however among the hypotheses formulated we note echolocation and buoyancy, with the former seeming to be the most probable.
It is a mixture of wax and triglycerides- the main constituent of which is wax.
Its acidity index is less than 2; its iodine number is also less than 3; the saponification index is between 105 and 120.
Formerly used in cosmetic creams, its use is now strictly regulated to prevent the massacre of whales and dolphins. It is replaced by jojoba wax.
Synthetic waxes
All of these waxes are the result of chemical processes.
- Fischer-Tropsch waxes
Invented in 1923 by the two chemists Franz Fischer and Hans Tropsch, the Fischer-Tropsch reaction is a reaction making it possible to manufacture a fuel.
A solid wax is obtained at room temperature, composed of linear alkanes, essentially accompanied by alkenes and small quantities of alcohols, aldehydes and esters.
This wax is hard and has a macrocrystalline structure comparable to that of natural paraffins.
It is used for the manufacture of adhesives, candles, sticks in the cosmetics industry and polishes.
- Polyethylene (or polypropylene) waxes
The low density polyethylene can be cracked at 400 ° C. A shorter chain polymer is obtained which has the characteristics of a wax, soluble in white spirit, turpentine, xylene and used in the manufacture of polishes, products for the maintenance of leather, adhesives etc.
- Polyethylene oxide waxes (or polypropylene oxide)
They are soluble in water, but also in certain organic solvents.
They are used in the cosmetics industry, but also as a coating agent for fruits and to shine car bodies during washing.
Polishes
Polishes are wax-based preparations, most of the time containing a coloring substance and various additives, intended for the maintenance of leather.
Originally they are formed of fatty substances which keep the leather supple; the color black (most leathers had this color) is given by carbon black.
Gradually we use beeswax more or less diluted in turpentine according to the consistency we want to give it to facilitate its spreading.
Today shoe polish is a complex preparation that can contain natural, animal (beeswax) and / or vegetable waxes, but also synthetic waxes (polyethylene waxes), silicones sometimes for water resistance and ‘waterproofing of leathers, solvents (white spirit mixed with turpentine) and various synthetic dyes although carbon black is still sometimes used for black.
Oils
What is the difference between oil and wax?
Both waxes and oils are lipids with hydrophobic properties, but their difference is not simply a difference in physical state: liquid or solid, at room temperature.
Their difference is chemical: The oil, liquid at room temperature, is composed of triglycerides, ie a combination of 3 fatty acids (R-COOH) for a molecule of glycerol also called glycerin (CH2OH – CHOH – CH2OH).
Wax, solid at room temperature (except jojoba wax, unfairly qualified as oil) is composed of esters (R-COO-R ‘): reaction between an alcohol (R’-OH) and a single fatty acid ( R-COOH).
Its physico-chemical properties are therefore different from an oil and in particular much more stable.
This is the reason why waxes do not go rancid, unlike oils.